Arsenic (As)-Resistant Endophytic Bacteria Isolated from Ferns Growing in As-Contaminated Areas

Abstract

In this study, As-resistant endophytic bacteria (AEB) from four different ferns (i.e., Pteris vittata, Pityrogramma calomelanos, Blenchum orientale, and Nephrolepis exaltata) collected from the polymetallic mine (Nui Phao) in Vietnam were isolated and characterized. The sampling locations were contaminated with As concentration within the range of 316–1606 mg kg^–1. A total of 5 arsenite(III)- and 26 arsenate(V)-resistant endophytic bacterial strains that belonged to 13 different genera were obtained. The most predominant isolate (accounting for 36% of the total isolated AEB in root ferns) was identified as Bacillus sp. The isolates were more resistant to As(V) than to As(III). Among As(V)-resistant strains, 26 were resistant to As(V) at concentrations of 80–320 mM, whereas 5 As(III)-resistant strains were able to tolerate As(III) of up to 160 mM. Although all the isolates had the ability to produce indole acetic acid (IAA), only three strains (i.e., Sporosarcina luteola R3.3.1, Paenibacillus sp. R3.8.3, and Acinetobacter sp. L2.5.1) had the phosphate-solubilizing ability. The pot experiments using P. vittata and inoculation of the four selected AEB (i.e., Priestia megaterium R2.5.2, Micrococcus luteus S3.4.1, P. megaterium R3.4.5, and P. megaterium L3.5.1) confirmed the important role of AEB in plant growth promotion and phytoremediation potential of As-contaminated soils.